Charge-to-mass Ratio of Saltating Particles in Wind-Blown Sand

Abstract

The electrification of sand particles plays an important role in aeolian events. In this paper, the charge-to-mass ratio vertical profiles of saltating particles in wind-blown sand were measured by a field experiments. By combining the results of field measurements with our previous wind-tunnel measurements, we discussed the factors affecting the charge-to-mass ratio of saltating particles. It reveals that the magnitude of the charge-to-mass ratio increases exponentially with height above the surface. In addition, the charge polarity of saltating particles depends on the relative size between saltating and creeping particles, and the magnitude of charge-to-mass ratio is determined by wind velocity and the relative size difference ratio between saltating and creeping particles.

Applications of Electrified Dust and Dust Devil Electrodynamics to Martian Atmospheric Electricity

“…There is less success in establishing expected/limiting values. In aeolian sand transport studies values have been quoted of order 60 µC kg −1 , (Schmidt et al 1998;Zheng et al 2003Zheng et al , 2004Bo et al 2014). In gas-solid pipe flows continuous sand transport is performed while measuring the current to metal pipe, here values of order 3 mC kg −1 have been measured (Matsusaka et al 2010).…”

“…In laboratory experiments of sand transport in the absence of dust, it has been seen that sand may electrify either positively or negatively depending on the size distribution within the sand bed (Bo et al 2014;Zheng et al 2003, Kok and Renno 2008a, 2008b. Laboratory experiments have also shown that dust re-suspension in the absence of sand shows little net (size dependent) dust electrification , however the role of dust aggregates (acting like large sand-sized particles) could possibly complicate this behaviour.…”

“…Modelling has been unsuccessful in satisfactorily explaining this size dependence in contact electrification, although several promising models are being pursued. For example, one model is based upon electron transfer through so-called high energy electron surface states (Lacks and Sankaran 2011;Apodaca et al 2010;Bo et al 2014). It would be extremely useful here to experimentally identify the precise charge/polarity dependence of contact electrification with grain size: this has yet to be done.…”

“…Despite this, some success has been achieved with electron transfer models involving electron donor/acceptors or so called high energy electron states in insulator-insulator contact, (also known as a molecular ion state model) (Lowell and Rose-Innes 1980;Bailey 2001;Duke and Fabish 1978). Similar electron transfer models involving so-called high energy surface electron states (likely due to impurities/contamination) are used in describing size dependent electrification (Lacks and Sankaran 2011;Bo et al 2014).…”

“…In these experiments sand grain electrification was measured in a conventional manner using an Faraday cup type electrode to collect the charge of impacting grains and an electrometer to quantify the discharging current (Bo et al 2014).…”